A new study fuels the ongoing debate over the health risks of bicycle riding for men: Researchers found that cyclists who bike more may face a higher risk of prostate cancer, but not a greater chance of infertility or erectile dysfunction. The findings aren't definitive, and they conflict with previous research on impotence and infertility. Other experts pointed to the study's weaknesses, and lead author Dr. Milo Hollingworth, a research associate at University College London, acknowledged that the findings are "difficult to interpret."